Automatic control apparatus for air supplied hydrofoils mounted at a watercraft



United States Patent inventor Hanna von Schertel Sonnenberg, l-lergiswil, Switzerland Appl. No. 774,965 Filed Nov. 12., 1968 Patented Dec. 8, 1970 Assignee Supramar A.G.

Luzern, Switzerland a corporation of Switzerland Priority March 8, 1968 Germany No. 81,556,832

AUTOMATIC CONTROL APPARATUS FOR AIR SUPPLIED HYDROFOILS MOUNTED AT A WATERCRAFT 11 Claims, 8 Drawing Figs.

11.5. CI. 114/665 lnt. B63b 1/18 Field ofSearch..... 1l4/665A References Cited UNITED STATES PATENTS 3,103,197 9/1963 von Schertel l14/66.5 1/1964 von Schertel 114/665 Isa 46 4c Primary Examiner-Andrew Farrell Attorney Werner W. Kleeman ABSTRACT: There is disclosed for a hydrofoil mounted to a watercraft, a control apparatus for automatically maintaining the immersion depth of the hydrofoil. This control apparatus comprises air control valve means provided for the hydrofoil in order to influence lift by admitting a controlled quantity of air to the surface of said hydrofoil, and there are means providing a number of suction openings arranged above one another, partially above and partially below the normal water level during cruising. The suction openings function as command elements. Additionally, there isprovided self-enclosed control body means capable of being contracted, a respective conduit for connecting each suction opening individually with said control body means in such a manner that the suction force prevailing at each suction opening appearing below the i water level shortens the length of said control body means by a respective predetermined unit of length, said control body means including a movable portion operably connected with said air control valve means such that said movable portion of said control body means actuates the air control valve means in its closing direction.

BACKGROUND OF THE lNvENr oN The present inventionrelates to an improved controlap paratus for automatically maintaining the immersion or submersion depth of hydrofoils mounted at a watercraft, wherein the lift of such hydrofoils is influenced by admitting to the foil surface a quantity of air which can be controlled by a valve unit, and furthenwherein, superimposed suction openings, serving as command elements, arranged partially above and partially below the normal level of the water during cruising,

are preferably arranged at a support strut forthe foil.

another which opened intoacompartment communicating with air exit or discharge openings provided at the foil. The quantity of air entering the foil is therefore dependent upon .the number of air inlet openings which, at any instant of time,

are above the water level. This type of apparatus, which is quite simple in construction, has, however, the drawbacks,

that, just as in British Pat. No. 1,052,305, there is not possible The inventioncan be employed with completely submerged hydrofoils which by themselves do not maintain any stable position, or at foils which during cruising have portions disposed above the water level, yet are not large enough to insure for self-stability, or at partially immersed foils where the immersion depth stability is completely or periodically increased, for instance during travel with the sea astern.

In known prior art control devices for automatically maintaining the submersion depth, foils or flaps adjustable in their angle of attack are pivotably mounted at the rear edge of the hydrofoil and serve as a meansfor influencing lift. Changes in the angle of attack or pivoting of the flaps can be performed bymeans of hydraulic servomotors receiving their command signals by mechanical, electrical, or hydrostatic (hydraulic or pneumatic) sensors. Suitable as an electrical sensor are switches arranged above one another, completing acurrent circuit when they are immersed} or ultrasonic devices which measure the emersion or surfacing of the vehicle or craft. Such type installations, requiring for their operation two sources of energy, are complicated and, correspondingly, liable to malfunction. In German Pat. No. 1,1 13,878, there is disclosed as a hydrostatic sensor a group of Pitot tubes arranged above one another which point in the direction of travel, and which when submerged or immersed measure the pressure head. Although this apparatus'is not complex in construction, practical experience therewith liasshown that the Pitot tubes easily tend to become clogged by substances dissolved in the Water or foreign bodies floating around in such water, so that stability disturbances occur.

According to British Pat. No. 1,052,305, the sensor is provided by superimposed suction openings which are partially above and partially below the normal water level. All of these suction openings communicate with a single compartment in which there occurs a change in the negative or s ubpressure during craft travel as a function "of the number of submerged suction openings, and thereby, causes actuation of a foil flap.

Also, this device is less complicated than electronic controls; however, trial runs in basins or tanks and experiments with the watercraft have shown that it is hardly possible to obtain pressure changes which are linearly dependent upon the immersion depth. Additionally, the control device is affected by oblique flow (waves and turns). Moreover, the addition of command signalsof other sensors responsive to motions of the draft, for instance rate gyros and accelerometers, can only occur in an incomplete nonlinear fashion. a The suction openings must be relatively large in order to maintain a short enough response time. h 1

The control apparatus according to the present invention differs basically from the previously mentioned devices in that it does not control the angle of attack of thefoil or a foil flap, rather controls the quantity of air delivered to the hydrofoil, to

any faultless addition of the control signals from other sensors,

that previously in practice it wasnot possible to obtain any linearity of the changes in lift with the immersion depth, and that the entering quantity of airwas influenced by inclined currents. a

SUMMARY or THE INVENTION Accordingly, it is a primary object of the present invention to provide an improved automatic control apparatus for hydrofoils which overcomes the aforementioned drawbacks of the prior art structures.

Another, more specific object of the present invention is the provision of an improved automatic control apparatus for air without error. Practical experience: has shown that a watercraft equipped with a control device of the present invention behaves faultlessly in waves and that the previously mentioned defects are not associated therewith. In contrast to electronic control devices, the control apparatus of the present invention, which does not require any source of energy for its operation, is much simpler and, therefore, also more reliable in operation. a

The present invention resides in the features that with a control apparatus of the previously mentioned type each suction opening is individually connected through the agency of a respective conduit with a self-enclosed control body means capable of being pushed together. The connection takesplace in amanner such that the suction force occurring at each suction opening below the water level shortens the length of the control body means by .a respective predetermined unit of length. Furthermore, the movable portion of the control body means is connected with the air-control valve unit in such a way that preferably with the interconnection of a suitable amplifier, the air control valve unit is thus moved in its closing direction.

The invention will be described hereinafter by way of illustration in connection with FIGS. 1 to 5. It should be recognized that the control bodymeans, according to one embodiment, is constructed as a cylinder with an insertable piston member and, according to another embodiment, consists of a which can be contracted. It is possible with each embodiment to actuate an air control valve unit in an analogous manner.

thereby influence lift. This system is alreadymuch simpler in h its basic concept than those previously described, and the forces required for actuating the valve controlling the quantity of air only amount to a small fraction. of that necessary for moving a foil or parts thereof. Previously, ther known, for air-controlled foils, an arrangement sit in U.S. Pat. No. 3,117,546, in-which the imm feeler possessed air entry openings arrange DESCRIPTION OF THE DRAWINGS The invention .will be better understood, and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such descriptionmakes reference tothe annexed first embodiment of inventive control apparatus in which the control body is provided with a displaceable piston member,

and wherein, in Ol'dflftO simplify the illustration, the strut means and the hydrofoil have been shown on a much smaller scale than the control body;

FIG. la is a sectional view showing the streamlined profile of the supporting strut for the hydrofoil;

FIG. 2 is a schematic view, again partly in cross section, of a 7 further embodiment of inventive control apparatus utilizing a control body provided with a displaceable or insertable piston member;

FIG. 3 schematically illustrates, partly in cross section, a control apparatus having elastic control bodies which can be contracted and which are arranged behind one another;

FIG. 3a illustrates a variant of the control body used in the arrangement of FIG. 3;

FIG. 4 is an alternative embodiment, shown in cross section, of the control body of FIG. 3, wherein the left-hand half of the control body is cut at an angle of 90 to the right-hand half thereof;

FIG. illustrates in sectional view an alternative embodiment of the control body of FIG. 1 wherein the principle underlying this embodiment also applies to the control body of FIG. 2; and

FIG. 5a is a plan view of a disc ring used in the control body of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Describing now the drawings, in FIG. 1 there is shown a control body consisting of a cylinder 1 and a sliding piston member 2 arranged within such cylinder. An optional number of inlet openings 3a to 3e, arranged above one another, are provided at the wall In of the cylinder 1, these openings 31: to 3e having the same spacing from one another. Inlet openings 3a to 3e are connected via conduits 4a to 4e, respectively, with suction openings 5a to 5e, respectively, provided at a support strut 6. FIG. Ia illustrates the profile of the support strut 6 providing a connecting member between the hull of the watercraft and the hydrofoil 7. During cruising, the currents or flow at both sides of the profile of the strut 6 generate a subpressure or negative pressure, so that air will be sucked out of the cylinder chamber or compartment lb by those suction openings which are submerged. Moreover, it should be understood that the suction openings 50 to 5e can be all arranged at the same side of the strut 6 or in alternating fashion at both sides thereof.

Considering now details of the piston member 2, it will be recognized that such incorporates the piston base or floor portion 8 and the piston wall or skirt 9, the length of which, in the illustrated terminal position with the air control valve unit 13 completely opened, covers all of the inlet openings 3a to 3e. Furthermore, a slot or port 10 is provided above the piston base 8, the height of which is equal to the spacing of the inlet openings 3a to Sc. A spring member 11 biases the piston member 2 in the direction of the inlet opening 3a, which communicates with the lowermost suction opening 5a at the strut 6, against a stop or impact member 12. These inlet openings 3a to 3e are arranged in such a way that in this terminal position of the piston member 2 the central region of the lowermost opening 3a approximately aligns with the upper edge of the slot or port 10.

The piston member 2 is rigidly connected directly, or through the agency of a suitable amplifier 14, with the air-control valve unit 13. This valve unit 13 regulates the quantity of 1 air entering into the foil channel 15. Channel 15 communicates via the air discharge openings 16 with the upper surface of the hydrofoil 7. Owing to the negative or subpressure prevailing at the foil during cruising, the air will be sucked out of the-discharge openings 16.

The described control apparatus functions as follows: The depicted terminal position of the piston member 2 corresponds to the maximum emersion or surfacing of the strut 6, in other words, the smallest immersion or submersion of the foil, during which time all of the suction openings 5a to 5e are disposed above the water level WL. Since the valve unit 13 is completely open, the largest quantity of air is admitted to the foil 7 and the smallest lift is attained. Now, if the immersion depth of the foil 7 increases and if the suction opening 5a drops beneath the water level WL, then the negative or subpressure prevailing at this opening Sawill be transmitted via the conduit 40 and the slot or aperture 10 to the cylinder compartment 1b. The piston member 2 will be raised against the force of the spring 11, so that the slot 10 frees the inlet opening 3b which communicates via the conduit 4b with the suction opening 5b which is still above the level of the water. The subpressure in the cylinder compartment lb drops because of the admission of air via the opening 5b and the piston member 2 will only move upwardly to such an extent until the subpressure has dropped to a degree such that the force or pressure on the piston maintains the equilibrium of the spring force. The valve unit 13 is closed by the amount of the movement of the piston member 2 and the lift increases at the foil 7. If during a further increase of the immersion depth the suction opening 5b also falls below the level of the water WL, then the subpressure once again increases and the piston member 2 again moves through the same path as previously, towards the top until, on account of a reduction of the subpressure, it stands still. The quantity of air flowing through the valve unit 13 is still further reduced and the lifi once again is increased. The closure path of the valve unit 13 is therefore proportional to the number of submerged suction openings 5a to Sc. On the other hand, if a suction opening emerses or surfaces, so that air can be sucked through such, then the piston member 2 moves downwardly under the force of the spring 11 through the same path as previously, until the pressure upon the piston once again maintains the equilibrium of the spring force.

The inventive control apparatus is constructed in such a way and the hydrofoil designed in such a fashion that with an average immersion or submersion of the support strut 6, during which approximately the same number of suction openings are above as below the water level WL, an average quantity of air flows to the foil 7. Such generates an average lift corresponding to the weight of the watercraft. Upon deviating from this average immersion depth, there automatically occurs a reduction of the lift when the foil 7 approaches the water level, and during an increase of its immersion depth this lift is increased, so that the immersion depth of the foil is regulated with respect to the water level WL.

The embodiment of FIG. 2 operates along the same principle as the control apparatus described in conjunction with FIG. 1. However, in this-case, the control of the inlet openings 3a to 3e is not undertaken by means of the piston member 2, rather by a hollow piston rod 17, also sometimes conveniently referred to as a slide member, which is coupled with the piston member 2. This hollow slide member 17, similar to the previously described embodiment possesses a slot or port 10 through which air can be withdrawn or delivered to the cylinder compartment lb through the agency of the hollow slide member 17 and the openings or apertures 18. The piston member 2 is preferably sealed by a so-called rolling membrane or diaphragm 2a.

This embodiment of the invention provides the advantage that the friction surfaces of the slide member 17 are considerably smaller than those of the piston member 2 of the construction of FIG. 1. In fact, the piston member 2 in FIG. 2 is practically free of friction. The effective piston surface in FIG. 2 can be the same or greater than that of FIG. 1, so that the piston force with respect to the friction surface can be greater by a multiple than in FIG. 1. Consequently, the piston force can overcome periodic starting difficulties of the slide member 17, which in FIG. 1 can result in faulty control. Such starting difficulties can occur because of dust, soiling, and especially due to salt deposits of the sea water. It should be understood that a small quantity of water continuously circulates from the lowermost emersed or surfaced suction opening still located in the spray water of the support strut 6 towards the uppermost immersed opening. During standstill of the craft, the residual water dries, leaving a deposit which, during the beginning of cruising initially brings about an increase in friction until it is again dissolved by the entering water. A further t advantage of the embodiment of FIG. 2.is that the entering or admitted water can flow away by means of a downwardly opening guide 19. The slide member 17 retains those inlet openings 3a to 3e closed 'which lead to submerged suction openings 5a to Sc respectively, whereas in the embodiment of FIG. 1, the same are freed by .theupwardly travelling piston, so that air can discharge'by means of the submerged openings in the presence of a small increase in resistance.

In the embodiment of FIG. 2,'the restoring force in the opening direction of the valve is not attained by means of a spring 11 as in FIG. 1, rather by means of a piston20 which has approximately half of the surface of the piston 2 and which travels or reciprocates in a cylinder 21. A suction force acts upon the piston 20, which is generated by the flow at a suction opening 22 of the support strut 6 and whichis conducted by means of the conduit 23 to the cylinder compartment 21a. This arrangement has the advantage that the restoring force just as the actuation force. (therefore also the reaction speed of the control) increases as a square of the velocity of the watercraft. Since a negative or subpressure continuously prevails in the cylinder 21, in this case there cannot occur any soiling of the running surfaces;

According to the embodimentof Flg. 3, the control elements 24a to 24f of the control body are elastically contractible, and wherein the sidewalls 25 are resilient or flexible. In FIG. 4, the control elements 24 are, in each instance, closed by a cover member 26 and a rubber or metallic membrane 27. The control elements are connected with one another in a manner such that during their actuation, their paths of dis placement add and the sum of these paths is transmitted to the valve unit 13 and, if desired, through the agency of an intermediate connected amplifier 14.

Considering now the embodiment of FIG. 3 in greater detail, it will be seen that the flexible sidewalls 25 of each control element 24a to 24f consist of a bellows, for instance formed of rubber, which in self-sealing fashion is pulledover the cover plate 28 and there again held by the intermediate.

plate-29 or theintermediate body member 30. Each such intermediate body member 30 possesses tworespective inlet openings 3a to 3f with connections or conduits, as shown, leading to both neighboring control elements 24a to 24f. In FIG. 4 the admission of air takes place through the rigid sidewalls of the control elements. i

The return or restoration in the direction of opening of the valve unit 13 again takes place in both embodiments, either by means of a piston member 20 (FIG. 3) which is subjected to a suction force or by a spring 11 (FIG. 4). If the control elements 24, as illustrated, are free of pressure, then they will be pressed against the impact or stop means 31 by the restoring force of the piston 20 or the spring 11. The path in the direction of closing is limited by the stop or impact member 32 for each control element. In FIG. 4, the left-hand portion of which is a section cut at an angle of 90 with respect to the right-hand portion, there 'are provided at both sides, analogous to the arrangement of FIG. 3, the impact or stop members 31 and 32 for limiting the displacement path. The impact members 31, 32 for limiting the displacement path can also be situated internally of the control element, as shown for instance in the embodiment of FIG. 3a. If a suction opening 5a to 5f enters beneath the water level WL, so that a suction force appears thereat, then the control element communicating therewith will be contracted by virtue of the subpressure prevailing therein, and specifically, through the .path determined by the stop or impact members. The closure path of the valve unit 13 corresponds to the sum of the paths of the contracted control elements. The function of the control device or apparatus according to FIGS..3 and 4 is therefore the same as that considered inconnection with FIGS. 1 and 2.

Each suction opening 5a to 5f is separately connected via a conduit 4a to 4f, respectively, with a control element, whereby a portion of each conduit 4a to 4]" must be constructed to be flexible, for instance by using hose conduits, in order to be able to partake in the movements of the control elements.

In order to maintain the reaction or response speed of the I control large it is desirable to have small control paths, that is to say, the path of the piston 2 in FIGS. 1 and 2 from one inlet opening, for instance, the inlet opening 3a to the next, for instance, inlet opening 3b, will be retained in the order of magnitude of 0.5 to 2 millimeters. 0n the other hand, the inner diameter of the inlet openings 30 to 32 and the conduits 4a to 4e for the above example must exceed 2 millimeters (the outer diameter greater than 3 millimeters), in order to maintain the quantity of air sufficiently large and the power losses small.

Consequently, the difficulty exists that the connections of the conduits 4a 10 4e in the practical construction cannot be undertaken for reasons of geometry according to the arrangement of FIGS. 1 and 2. The solution of this problem is best illustrated by way of example in FIG. 5, in which the path of a ,stage can be held small, even with larger conduit diameters,

diameter than the discs 33 and are each provided with a slot 35. The slot 35 is angularly displaced, for instance through 30 with respect to the next situated slot, so that all slots are disposed along a spiral. At the location of each slot, in other words, at the same convolution or spiral, there is provided at the jacket a respective opening or bore 3, corresponding to the previously considered openings 3a to 3e, the diameter of which is somewhat smaller than the sum of the height of one disc 34 and two discs 33. A respective conduit 4, corresponding to the previously considered conduits 4a to 42, is coupled with each bore 3a to 3e,,respectively. The air is therefore withdrawn anddelivered via the slot 35 and the annular gap existing between the piston 2 or slide 17 and the ring 34, so that the pressure can distribute evenly or uniformly about the piston and no lateral forces can occur thereat. Above the r egion of the bores 3 (or 3a to 3e).there: are inserted further an t nular discs 33 for guiding the piston 2 or slide 17 and which are spaced from one another by rings 36. All rings are pressed together by means of a suitable cover member 37.

. present in the embodiments of FIGS. 3 and 4.

It should be apparent from theforegoing detailed descrip- The above-described problem for the delivery of tion, that the objects set forth at the outset to the specification have been successfully achieved.

I claim:

1. In combination with a hydrofoil mounted to a watercraft, a control apparatus for automatically maintaining the immersion depth of the hydrofoil comprising air control valve means provided for said hydrofoil in order to influence lift by admitting a controlled quantity of air to the surface of said hydrofoil, means providing a number of suction openings ar ranged above one another, partially above and partially below the normal water level during cruising, said suction openings functioning as command elements, self-enclosed control body means comprising control chamber means capable of 'being contracted, a respective conduit for connectingeach suction opening individually with said control chamber means in such ,a manner that the suction force prevailing at each suction opening appearing below the water level shortens the length of said control chamber means by a respective predetermined unit of length, said control body means including a movable portion operably connected with said air-control valve means such that said movable portion of said control body means actuates said air-control valve means in its closing direction when said control chamber means is being contracted.

2. The combination as defined in claim 1, further including support strut means for connecting the hydrofoil with the t air is not t watercraft, said means providing said suction openings being located at said support strut means,

3. The combination as defined in claim 1, wherein said control body means further comprises a cylinder at which there are arranged at a uniform spacing above one another the con duits for said suction openings, said conduits having inlet openings which open in the same sequence as the suction openings arranged above one another, said movable portion of said control body means embodying a piston member located in said cylinder, said piston member having a piston base directed in the direction of the lower most conduit, said piston member further including a pistonwall having a length capable of covering said inlet openings of all of said conduits, said piston wall possessing a slot directly above said piston base, the width of said slot being equal to the spacing of said inlet openings of said conduits from one another, and means for applying to the piston member a force which acts opposite to the suction force, said piston member being operably connected with said air-control valve means.

4. The combination as defined in claim 1, wherein said control body means comprises a first cylinder having a cylinder compartment, a piston member located in said first cylinder, said movable portion of said control body means embodying a hollow piston rod connected with said piston member, said hollow piston rod having at least one outlet directed toward said cylinder compartment of said first cylinder, a second cylinder of smaller diameter, said piston rod moving in said second cylinder, said conduits for said suction openings having inlet openings and being arranged at an equal spacing from one another at said second cylinder and opening in the same sequence as the suction openings disposed above one another, said piston rod having a slot at the region of its end directed towards said second cylinder, the width of said slot being equal tothe spacing of said inlet openings of said conduits, and means for subjecting said piston member to a force which is opposite to the suction force, said piston member being operably connected with said air-control valve means.

as a running surface for such piston member, whereas each respective intermediate disposed ring disc means possesses a greater internal diameter than the diameter of said, piston member and further incorporates a respective slot, said inlet openings of said conduits for said suction openings in each instance opening at the wall of said cylinder at the location of their associated slot, said slots of said ring disc means being angularly offset with respect to one another in a substantially spirallike configuration, and cover means for sealingly pressing together all of said ring disc means.

7. The combination as defined in claim 1, wherein said control body means comprise a number of individually interconnected elastic self-enclosed control elements which can be contracted and corresponding in number to the number of said suction openings, each control element being individually connected via a respective one of said conduits with a suction opening, each control element possessing stop means for its greatest and smallest length, means for subjecting the entire group of control elements to a force acting opposite to the suction force, said group of control elements operably communicating with said air-control valve means.

8. The combination as defined in claim 7, wherein each control element has sidewalls formed as bellow means.

9. The combination as defined in claim 7, wherein each control element is provided with a cover member formed of an elastic membrane.

10. The combination as defined in claim 4, further including a support strut for connecting the hydrofoil with the watercraft, said support strut having a suction opening, said means for subjecting said piston member to a force acting opposite the suction force prevailing in the control body means comprises a further cylinder and a further piston member travelling in said further cylinder, said further piston member having approximately half the surface of said piston member in said first cylinder and being operably coupled therewith, said further cylinder having its cylinder compartment connected with said suction opening provided at said support strut through the agency of a conduit means.

11. The combination as defined in claim 7, further including a support strut for connecting the hydrofoil with the watercraft, said support strut having a suction opening, said means for subjecting said group of control elements to a force acting opposite the suction force prevailing in the control body means comprises a cylinder and a piston member travelling in said cylinder, said piston member having approximately half the surface of said control elements and being operably coupled therewith, said cylinder having its cylinder compartment connected with said suction opening provided at said support strut through the agency of a conduit means. 

